Technical Field
Exemplary aspects of the present invention generally relate to an image forming apparatus.
Related Art
Image forming apparatuses are known that include a transfer bias output device to output a superimposed bias as a transfer bias in which an alternating current bias and a direct current bias are superimposed. In the image forming apparatuses of this kind, toner images formed on photoconductors through known electrophotographic process are primarily transferred onto a belt-type intermediate transfer member (hereinafter, intermediate transfer belt) and then secondarily onto a recording medium in a secondary transfer nip at which a contact roller contacts a front surface of the intermediate transfer belt. A back surface roller contacts a back surface of the intermediate transfer belt to interpose the intermediate transfer belt between the contact roller and the back surface roller. To secondarily transfer the toner image through known electrostatic transfer process, a secondary transfer bias is applied to the back surface roller while the back surface roller contacts the back surface of the intermediate transfer belt. To enhance secondary transfer ability, a superimposed bias, in which an alternating current (AC) voltage and a direct current (DC) voltage are superimposed, is output as the secondary transfer bias.
However, in the image forming apparatus that utilizes the superimposed bias as the secondary transfer bias, transfer failure may occur specifically when at least either the temperature or humidity is high.